1. Field of the Invention
Aspects of the present invention relate to a battery pack, and more particularly, to a battery pack in which a coupling part of a case that is formed to enclose a bare cell is closely contacted to prevent a molding being inferior due to a molding material leaking from the coupling part of the case during the molding using resin or hot melt.
2. Description of the Related Art
Recently, compact and portable electronic/electric appliances, such as, cellular phones, lap-top computers, camcorders, and so on, have been actively developed and produced, and require battery packs for portable operations. In consideration of economical concerns, a battery pack generally includes a secondary battery that is rechargeable, such as, a nickel-cadmium (Ni—Cd) battery, a nickel-hydrogen (Ni-MH) battery, and a lithium (Li) battery.
Battery packs including an Li secondary battery are widely used for the portable electronic/electric appliances. The Li secondary battery is used because an Li secondary battery has an operating voltage three times larger than that of the Ni—Cd battery or the Ni-MH battery, and an energy density per unit weight larger than that of the Ni—Cd battery or the Ni-MH battery. An Li secondary battery may be classified as an Li ion battery using a liquid electrolyte, and a Li polymer battery using polymer electrolyte, according to the type of electrolyte used. The Li secondary battery can also be classified according to shape, for example, as a cylindrical Li battery, a rectangular Li battery, and a pouch-type Li battery.
A battery pack using an Li secondary battery includes a bare cell and a protecting circuit board electrically connected to the bare cell, to prevent the bare cell from being excessively discharged and overcharged. In order to attach the bare cell and the protecting circuit board, a molding process is usually performed. The molding process fills a space formed between the bare cell and the protecting circuit board using molding material such as, a resin, a hot melt, and so on. Here, the bare cell is fabricated such that in an electrode assembly, including a positive electrode plate and a negative electrode plate, electrode taps are connected to electrode collectors, which are coated with an electrode active material, and a separator disposed between the positive electrode plate and the negative electrode plate. The bare cell is disposed in an open-topped can. The opened top of the can is sealed by a cap assembly.
When strength of the battery pack is reinforced to protect the bare cell from exterior impacts by enclosing the outer side of the bare cell, the case is physically coupled to improve the reliability of the bare cell. However, the case is not completely coupled at coupling parts, so that the molding material leaks from the coupling parts and causes an inferiority molding of the battery pack.